You could also send a PM to kojn, maybe he shares his config. He's called kojjn on the forums IIRC.

Note that the "edge effect" was added later during video editing, and can't be reproduced ingame. (Which is unfortunate, I would love to have something like that in Xonotic!)

Quick addendum: MrBougo pointed out a more or less similar effect which can be enabled ingame, see http://forums.xonotic.org/showthread.php?tid=4201 (the effect is also used if you pick up strength and have postprocessing enabled). I played around a bit with the settings, here's how it looks:

I will set up a thread either tonight or tomorrow night on how to achieve the effect, along with how to set the config up.
Seems a few people have been interested in this and the simpleitems pk3 which I still have (thanks to Machine for this).

Whoever posted the screenshot has indeed came close, would look similar with the config settings I used I think

The effect has been achieved by post processing effects in premiere pro, but can be done almost the same as shown in the screenshot in this thread.